Packing for steam turbines



Nov. 5,

K. RODER f 2,220,616 PACKING FOR STEAM TURBINES I Filed Feb. 27, 1957 5Sheets-Sheet l Nov-5,1940. A'K DgR v2,220,616

PACKING FOR STEAM TURBINES' Filed Feb. 27, 1957 5 Sheets-Sheet 2 K.RGDER l PACKING FOR STEAM :umanms Filed Feb. 27, i937" Nov. 5; 1940.-

5 Sheets-Sheet 3 Nov. 5, 1940 K. RODER PACKING FOR STEAM TURBINES' FiledFeb. 27, 1937 5 Sheds-Sheet 4 Patented Nov. 5, 1940 UNITED STATES2,220,616 PACKING FOR. vSTEAM TURBINES Karl Riider, Hanover, GermanyApplication February 27, 1937, Serial No. 128,18 In Germany February 29,1936 My invention relates to improvements in packings for steamturbines.

The efllciency and reliability of a steam turbine depends to a greatextent upon the packings employed therefor. This applies particularly tomachines dealing with small volumes of steam, for instance, also tohigh-pressure parts of highpressure turbines.

Inthe labyrinth packings with projecting edges which are employed inmost cases, a circular sectional area of flow of small depth, namely thedepth of the clearance space, is left between the revolving part and thestationary part enclosing the same, which parts should not come intocon- 5 tact with one another.

This depth of the clearance space should be as small as possible andshould remain of the same magnitude over the entire peripheryindependently of the variation in pressures and tempera- 20 tures of theoperating fluid during the operation. It is theoretically possible tomaintain the clearance space as above mentioned strictly equal onlyinthe case in which both elements defining the clearance space presentexactly the same 25 operating conditions, such as is the case withpackings between the blade rims of turbines with nozzles and bladesrotating-in opposite directions.

All other packings, that is to say, the other packings employed inturbineswithnozzles and 30 blades rotating in opposite directions aswell as when employing packings of the usual type 2 40 only therevolving part retains its circular shape under all operatingconditions, whereas the stationary part loses its circular shape andcannot adapt itself, without producing mechanical stresses, tothevarying. temperatures, thereby 45 causing a reduction of theclearance space which impairs the reliability of operation.

The object of my invention is: to remove the above-mentioned drawbacks,i. e., to design and to assemble the stationary parts of an expansion 50or compression machine (by which are denoted steady flow machinesworking on the expansion principle, or on the compression principle, 1.e., turbines, or compressors, respectively) in such a manner I 55 (1)That the annular clearance space retains its circular shape under alloperating conditions; (2) That the expansion and contraction of theparts bounding the clearance space essentially produce enlargements ofthe clearance space only consequently, and 5 (3) That the temperatureand pressure variations do not entail any appreciable decrease of theclearance space so that the danger of contact of the movable parts iseliminated. To this end, it is above all necessary that the 10unavoidable departures of the machine casing from the circular form orfrom symmetry occurnot only on one side but symmetrically on oppositesides of the central axis, and that both casing parts have the sameshape and the same dimensions in planes transverse to the longitudinalaxis of the casing.

The invention is illustrated in the accompanying drawings, in which- IFigs. 1 and 2 are explanatory figures, and represent respectively inside and end elevation an unsymmetrical structure, showing thedistortion in dash lines, resulting from uneven expansion under theinfluence of heat and pressure.

Figs. 3 and 4 represent respectively in side and 'end'elevation asymmetrical structure according to the present invention, showing in.dash lines the symmetrical expansion under the influence v v of heat andpressure.

Figs. 5 to 10 show in sectional elevation diflEercut forms ofresiliently supporting the stator ring to prevent the transmission ofunavoidable casing distortions to the ring. 4

Fig. 7a is a transverse section through Fig. 7 on the line l in Fig. '7,and

Fig. 11 represents a steam temperature graph at dififerent'loads of athree-stage turbine. I

Referring to Figs. 1 and 2, these figures show a typical form ofanunsymmetrical machine casing A, having the connecting branches B and 40C located all on one side of a given central axial plane. Thedeformations of the casing, and also of its axis when subjected to hightemperatures in operation, are unsymmetrical, as indicated in dashlines. 5

Figs. 3 and 4 show in side and end elevation respectively the novelconstruction of a steam turbine casing in which correspondingly locatedpoints of thecasing on diametrically opposite 1 sides 0! thelongitudinal central axis depart from the circular shape to the sameextent (for instance, B, B; C, C), and in which the central axis D doesnot become dislocated or distorted. In other words, the unavoidabledeformations of the casing are symmetrical with respect to the centralaxis within all transverse sections of the casing.

While deformations of the casing are in this case not avoided, the axisof the casing is not deformed or shifted by these changes.

Furthermore those parts which support the guide blades and thestationary packing elements-even if these parts are subdivided in aplane through the longitudinal axis-should be made in the form of bodiesof revolution with respect to the casing axis, whatever their contourmay be in the direction of the axis, and be mounted in the casing insuch a manner that they may follow the changes in temperature as freebodies of revolution without loosing their circular shape.

To this end, such bodies of revolution may be supported by other bodiesof revolution which are concentrically mounted in the casing orassembled therewith so as to permit a symmetrical expansion orcontraction thereof in response to the temperature changes.

Referring first to Fig. 5, b represents in cross section one-half of therevolving part or rotor of the turbine which, of course, in itself is abody of revolution. The rotor carries the rotor blades 1'. In theturbine casing c, which may be of the general symmetrical character asshown in and described with reference to Figs. 3 and 4, is mounted thestator support d" which is annular and thus also constitutes a body ofrevolution. Support d" is shaped at one and d into a clamping ring andcarriesat the other end a separate clamping ring d. Between these twoclamping bodies of revolution is positioned the turbine stator a whichcarries the stator blades 3 and is in itself also a body of revolution.By this arrangement complete symmetry is maintained so that nodistortion, due to uneven heat expansion located in the upper half ofthe casing c and the other half of the elements is located in the lowerhalf of casing c. When these halves are assembled they act as completebodies of revolution and expand and contract symmetrically. This twoparts, for instance, four parts, provided the division lines are onplanes through the longitudinal turbine axis.

The form of the different bodies of revolution of which the entirestatoris composed as aforethe design requirements. For instance, as shown inFig. 6 at d1, (12, the clamping elements for the stator ring a may becomposed of two parts, each a body of revolution, and may hold thestator ring between them at its ends and at an annular rib a disposedintermediate its ends. Further, as shown in'Fig. 7, the stator ring amay be held by clamping rings d1, dz, as shown in Fig. 6, between one ofits ends and its middle, and its freely extending end may be held by aclamping ring 0' provided at an annular extension c" of casing c.

holds one end of the stator ring a by means of a ring 0' at the end ofan annular portion c" of casing C in a manner similar to that shown inFig. 7. The other end of stator ringa is supported by an annular supportt carried by the outer casing portion is through arms t'. The portion ofstator ring a intermediate its ends is held by an annular rib k oncasing portions k, whereby it is also prevented from longitudinalshifting.

Fig. 9 shows a construction similar to Fig. 8, except that one end ofthe stator ring a is carried by a separate supporting ring m mounted inthe casing portion C.

Fig. 10 shows the support of stator ring a at one end by means of aclamping ring dz attached by means of arms (is and a base ring d4 tocasing c. The other end of stator ring a is held by clamping ring c'supported similar to the manner shown in Fig. 7, and the stator ring ais supported intermediate its ends by a rib a held between base ringd4and a shoulder on casing c.

All of the holding or clamping rings for stator ring a, such as d, d inFig. 5, d1, dz in Figs. 6 and.

'7, c in Figs. 7, 8 and 10, and t in Figs. 8 and 9,

arms extending substantially in parallel to the turbine axis so thatthis stator support is made sufficiently resilient in radial directionto prevent unavoidable defprmations of the outer casing from beingtransmitted to the stator ring a.

The changes in temperature in the several stages of a turbine to beexpected may be seen from the graph, Fig. 11. It is assumed that theturbine under consideration be a three-stage turbine having a highpressure stage HD, a medium pressure stage MD, and a low pressure stageND. The turbine is divided into three stages.

The temperatures at the beginning and the end of these three stages areplotted in Fig. 11 against the load conditions varying within widelimits. The high-pressure HD and the medium pressure stage MD aresubjected as will be seen from Fig. 11 to great changes in thetemperature of the operating medium only when starting, the temperaturein this case increasing to a considerable extent from standstill tono-load running.

The changes in temperature during operation between no-load to full loadand back to standstill are relatively slight so that these variations intemperature during starting are only fractions of the great increase intemperature.

The temperatures of steam are not identical with the temperatures of themachine parts of the different stages; nevertheless it may be concluded'with certainty from Fig. 11 that the temdescribed may, of course, varyin accordance with peratures of the individual machine parts increaseconsiderably during and after starting and vary only to a slight extentduring operation.

in temperature occurring during operation should cause correspondingdecrease of the clearance space, the latter being only a smallpercentage of the former.

These conditions are actually obtained by the arrangement of thestationary elements of the machine, such as the stator ring and itssupporting elements in the manner shown in Figs. 5 to 10, in which theyare exposed to the steam temperature so that they can respond morequickly to variations in temperature than the adjacent .and having acasing enclosing said stator and Consequently, an

increase in the clearance space is brought about when putting theturbine into operation and when taking up a load, i. e., under operatingconditions which, in the designs followed hitherto, lead rather todecreases of the clearance by which the operation of the machine isendangered. In the present designs according to the invention, on theother hand, the decreases of the clearance space below that allowedduring the mounting of the machine, which occur duringthe operation ofthe machine at different loads, are so slight as to be practicallynegligible. Thus, in-assembling the machine, the allowable clearancespace between the moving elements may be made extremely small, and onlythe expansion oi! the rotor due to centrifugal forces need be taken intoconsiderationior the amounts of these clearances. I

The material for the revolving and stationary parts which limit theclearance space should have about the same coeflicicnt of heatexpansion. The dimensions, the wall thickness and the arrangement of thepacking parts in the path of the flowing medium depend upon theabove-mentioned method of designing steam turbines as will be seen fromFigs. 5 to 10.

I claim as my invention:

1. A fluid expansion or compression machine having a casing and statorand rotor elements subject to expansion and contraction, said casinghaving all portions deviating from circularshape with respect tothe'rotor axis arranged in pairs disposed symmetrically on diametricallyopposite sides of said axis, and having its stator elements mountedwithin said casing and formed as bodies of revolution with respect tosaid rotor axis, said stator elements comprising an elongated statorblade carrier and a plurality of rowsof stator blades mounted directlyon said carrier and being freely exposed to the varying temperatures ofthe operating'fluid and being disposed to tion disposed to hold saiddivided carrier together and to support it in said casing as a singlebody of revolution which retains its shape at Varying temperatures.

3. A steam turbine having a stator and a rotor rotor and beinglongitudinally divided in atleast one plane through the turbine rotoraxis, said and having a casing enclosing said stator and .rotor andbeing longitudinally divided in at least one plane through the turbinerotor axis, said stator comprising a similarly divided stator bladecarrier and a plurality of rows of stator blades disposed therein, saidblade carrier being constructed as a body of revolution with respect tosaid rotor axis, and at least one body of revolution diametricallydivided in a plane through said rotor axis but at right angles to thedividing plane of said carrier and disposed to hold said divided carriertogether and to support it in said casing as a single body of revolutionwhich retains its shape at varying temperatures.

5. A steam turbine having. a stator and a rotor and having a casingenclosing said stator and rotorand being longitudinally divided in atleast one plane through the turbine rotor axis, said stator comprising asimilarly divided stator blade carrier and a plurality of rows ofstator-blades disposed therein, said blade carrier being con- .structedas a body of revolution with respect-to said rotor axis, said casingcontaining at least one elastically centered body of revolution disposedto hold said divided carrier together and to support it in said casingas a single bodyof revolution which, retains its shape at varyingtemperatures.

6. A steam turbine having a stator and a rotor and having a casingenclosing said stator and rotor and being longitudinally divided in atleast one plane through the turbine rotor axis, said stator comprising asimilarly divided stator blade carrier and a plurality of rows of statorblades disposed therein, said blade carrier being constructed as a bodyof revolution with respect to said rotor axis, and at least one body ofrevolution disposed to hold said divided carrier together and to supportit in said casing as a single 'body of revolution which retains itsshape at varying temperatures, said carrier and said supporting bodybeing arranged in the path of the entering operating medium so as tofollow its temperature variations faster than the rotor elements of theturbine.

7. A steam turbine having a stator and a rotor and -having a casingenclosing said stator and rotor and being longitudinally divided in atleast one plane through the turbine rotor axis, said stator comprising asimilarly divided stator bla'de carrier and a plurality of rows ofstator blades disposed therein, said blade carrier being constructed asa body of revolution with respect to said rotor axis, and at least onebody of revolution disposed to hold said divided carrier together and tosupport it in said casing. as a single body of revolution which retainsits shape at varying temperatures, said carrier and said support- 8. Asteam turbine having astator and a rotor and having a casing enclosingsaid stator and rotor and being longitudinally divided in at lea-st oneplane through the turbine rotor axis, said stator. comprising asimilarly divided stator blade carrier anda plurality of rows of statorblades disposed therein, said blade carrier being constructedas a bodyof revolution with respect to said rotor axis, and at least one bodyoirevoluplane into two half shells and constructed as a body ofrevolution, a plurality of rows of stator blades disposed in saidcarrier, ring members clamping the two halves of the carrier togetherand maintaining the circular form of the carrier when variations of thelength of the carrier occur, said ring members comprising means engagingthe casing in a plane perpendicular to the rotor axis and intermediatethe ends of the carrier to support the carrier in the casing.

-KARL RGDER.

